In a cellular wireless system, a service area is divided into a number of coverage zones generally referred to as cells. Each cell may represent the wireless coverage area for a base station. Wireless terminals, including a wide range of mobile devices such as, e.g., cell phones and other mobile transmitters such as personal data assistants with wireless modems, may communicate with the base station via wireless links while located within the base station's cell. Multiple wireless terminals need to transmit different types of information with different priorities to the base station, e.g. various types of uplink traffic information, over the air link resources. The uplink air link resource may be defined as available bandwidth over time. The bandwidth is centrally controlled by the base station to avoid collisions between multiple wireless terminals who may wish to transmit at the same time. Each wireless terminal has an idea of its own current uplink traffic requirements, e.g., bandwidth over time required, quality of service required, priority level required for the information to be transmitted, time constraints on information to be transmitted, etc. The wireless terminals' uplink traffic requirements need to be conveyed to the base station, so that the base station can make informed decisions to assign uplink air link resources, schedule users, and send assignment messages notifying the wireless terminals of the choice that have been made.
Many known systems use a circuit switch approach to convey this exchange of uplink traffic information. In the circuit switched approach, the wireless terminal and base station typically exchange information over a control channel with a low bandwidth and a low bit rate, the exchange involves conveying requirements and requests from the wireless terminal to the base station, the negotiation of the amount of air link resource that can be allocated, and the assignment of the air link resource to the wireless terminal. Each transaction is generally slow and will require more than a few bits. This circuit switch approach typically will work well where the exchange can take place once at the beginning of a session, and the air link resource can be assigned for long intervals of time (e.g. 10 sec or 1 sec). In this approach you establish a link for an extended period of time and may send a message at the end of a session to relinquish the resource. Intervals of unused transmission time between the establishment of the link and the termination of the link represents wasted air link resources. This circuit switch approach ties up the air link resource for extended periods of time. With packet switch wireless systems, e.g. an OFDM system, this circuit switch approach is inefficient, as the wireless terminal generally do not need the air link resource for long contiguous segments, but rather need short durations, e.g., flash intervals. In addition, it is inefficient, in packet switch systems to be constantly have to renegotiate for a small amount of air link resource, as the overhead signaling becomes significant in relation to the amount of air link resource actually used for traffic.
Other more efficient approaches are possible which are better suited for packet type wireless communications systems, where each wireless terminal has a dedicated uplink channel with a dedicated amount of a air link resources for making uplink traffic requests at pre-determined times coordinated with the base station, and the base station makes assignments. This approach has a delay effect problem. There is a delay between when the wireless terminal transmits a request for uplink air link resources, and the time that a base station receives and processes the request. There is also a delay between the time when the base station generates and transmits the assignment and the wireless terminal receives and recognizes the assignment. These delays create misunderstandings between the base station and the wireless terminal resulting in wasted air link resources, unnecessary additional requests, and unnecessary additional assignments.
This problem of lack of understanding between the base station and wireless terminal becomes more complicated and new problems are created when multiple levels of priorities are considered. Assume that a wireless terminal needs a high levels of resources at a low priority level, e.g. a priority level associated with data, and needs low levels of resources at a high priority level, e.g., a priority level associated with voice. Depending on the timing, it is possible, that the low priority request information will be blocked indefinitely.
Certain information may be timing sensitive, e.g., if the request is not granted with an assignment within a specified time interval, the need for the request may go away. It is inefficient to transmit that requested data units are no longer needed. This dropping of requested data units unbeknown to the base station can result in misunderstanding and unnecessary wasted assignments by the base station. Also, some requests may be lost due to transmission errors, and there are trade-offs between whether to transmit another request immediately or whether to wait, since the wireless terminal does not know whether the base station never received the request or has not transmitted the assignment because of other higher priorities competing for the air link resource.
The needs and priorities within the wireless terminal can change between the request and reception of an assignment message allocating data units. Therefore, the wireless terminal may reallocate to a new priority level received air link resources that were originally intended for different (original) priorities when assigned by the base station. This can also result in misunderstandings between the base station and the wireless terminal.
In view of the above discussion, it should be appreciated that there is a need for improved methods of keeping track of air link resource requests in the case where the requests may correspond to multiple priority levels particularly in the context of signaling delays and potential loss of some transmitted requests and/or assignments. In particular there is a need for an understanding in the base station as to the wireless terminal uplink traffic needs and priorities, a need to maintain an understanding of the base station uplink traffic assignments in the wireless terminals, and/or a need for a methods and apparatus for conveying request information in a fast, efficient and timely manner utilizing a small number of bits so as to keep overhead low. There are also needs for methods that employ flexibility in allocating resources based on requests of various levels of priorities. Such methods should address the different problems presented by different priority users, as well as address concerns presented by lost request and assignment transmissions, and dynamic changes in needs at a wireless terminal. In the case of wireless terminals, there is a need for a method of maintaining an understanding of a base station's perception of a mobile's needs so that the mobile can effectively and efficiently update the base station's understanding in a timely manner.